Impregnating material for preserving wood



' out the fibrous structure thereof and combined Patented Mar. 26, 1940IBIPREGNATING MATERIAL FOR I PRESERVING WOOD Aaron Gordon, Berkeleyg C'alif.

A No Drawing. Application June 29, 1936, I Serial No.,87,939

6 Claims. (01. 134-785) I 2. Zinc sulphate '(ZhSOi) or any other zincThe present invention relates broadly to the protection of wood in itsraw'and finished state against wood attacking organisms, such as marineborer, termite and various other insects and fungi, and moreparticularly to an improved impregnating material which can beconveniently and efiectively applied to lumber, such as fence posts,railroad ties, pilings, telephone poles,-etc., to protect them againstdestructive agencies and at the same time render them resistant to fire.

. An object of the invention is to provide practical and effectiveimpregnating chemicals for wood which will deposit therein materialtoxic to wood destroying organisms and fungi.

Another object of the invention is to provide impregnating chemicals forthe preservation of wood which are efiectively distributed throughand/orprecipitated therein to render the Wood immune to attack by livingorganisms and more resistant to fire than when in its naturalstate.

While it is recognized that themarket ofiers a large number ofwoodpreservatives in which heavy metal salts are employed in'one form oranother to provide a toxic for wood destroyingly more permanent in theiraction than are the act with the products of hydrolysis in the event,

of leaching, and thus shift the chemical equilibrium back to theinsoluble metal salt or salts employed as the basic agency. In otherwords,

the present invention employs the common mass law principle and providesa preservative which is substantially non-leachableand consequently morepermanent in the wood than are the comparable Wood preservatives now onthemarket.

The impregnating material contemplated by this invention may consistessentially of aqueous ammonia and any metallic salts soluble therein.

As examples of these the following may be cited:

l. Copper sulphate (CuSOr) or any other copper salt and ammoniumphosphate ((NH4)3PO4) or any other phosphate in aqueous ammonia(NI-1401i).

salt in aqueous ammonia (NI-ROE).

and/or cobalt (Co) salts may be substituted for the above salts withoutdeparting from the rate, they precipitate and form a number of insolublesalts in the wood. In this manner the wood is' rendered immune to allwood destroying copper and. zinc salt combinations, the followingchemical combinations willbe formed in the tions set forth abovewill befound particularly PATE T OFFICE salt and ammonium phosphate ((NH4)3PO4) or any other phosphate in aqueous ammonia (NHQH).

3. Copper sulphate (CuSOi) or any other cop- 1 5. Zinc sulphate (ZDSOQor any other zinc salt and borax (Na2B4O7) or any other boron 6. Coppersulphate (CLISO4) or any other copper saltand borax (NazBiOvl or anyother boron salt in aqueous ammonia (NH4OH) In addition to the abovespecific examples, it will be understood that other combinations oftheabove may be used, and that nickel (Ni) spirit and scope of thisinvention) It has been found that when the above named salts or anycombination thereof are dissolved in aqueous ammonia (NI-E) and injectedinto 7 the wood and the ammonia is permitted to evapoorganisms, and atthe same time it is also ren-v dered fire resistant and improved in bothtensile and compressive strength.

When the wood is-impregnated with the above The CllNHPO. an the 'znnmeorcombinaefiective, due to the fact that they form salts which areinsoluble in water and. toxic to wood attacking organisms, and at thesame timethe. NH4PO4 radicals will render the wood fire resistant. Theselection of the basic .CuCOa and ZnCOa is. because these'are solubleinthe acidic I solution of the digestive juices in the wood attackingorganisms and thus liberate" the toxic. copper and zinc salts. At thesame time the CO3 radical renders the wood fire retardent, due

to the formation of CO2 in the presence of heat. v

In connection with the zinc borate (ZnBrO-z) and the copper borate(CuBrOv) combinations set forth above, it should be pointed out thatthese salts, while slightly soluble, are toxic to wood destroyingorganisms, and at the same time the borate radical (B407) will alsorender the wood fire retardent.

By the addition of an excess of Cu(OH) 2 and/or Zn(OH) 2, the metalsalts injected in the wood are rendered more permanent, as the excessCu(OI-I)2 and/or Zn(OH)2 and/or any other slightly soluble base willprevent hydrolysis of the precipitated salts. Thus should the CuNI-I4PO4undergo hydrolysis and. liberate a soluble phosphate, this will bereprecipitated by the base and be again rendered insoluble in water.

By way of an example in connection with the use of a basic zinccarbonate, it is pointed out that when the zinc carbonate impregnated inthe wood dissolves it will slowly form both zinc and carbonate ions, andthese ions will hydrolyze and produce a soluble carbonic acid which willleach out. However, by the provision of an excess of zinc hydroxide orother slightly soluble base, as suggested above, the latter will reactwith the soluble carbonic acid formed in the hydrolysis and thusreprecipitate the zinc carbonate. In other words, the zinc carbonate isnever lost, because the soluble part thereof is changed back, due to thepresence of the excess of zinc hydroxide or other base.

As the base I have used Cu(OH)2 and/or Zn(OH)2. These dissolved inammonia give the complex bases Cu(NH3)4(OH)2 and respectively. When theammonia evaporates ofi, these complex bases go back to the form Cu(OI-I)2 or Zn(OH)2, or to the oxides CuO or ZnO.

The copper complex hydroxide has a dissolving action on cellulose whichcauses the preservative Basic copper carbonate (CuCOsCu(OH)2) 10 Basiczinc carbonate (ZnCOs--Zn(OH)2) 10 Copper ammonium phosphate (CuNH4PO4)Zinc ammonium phosphate (ZIINI-I4PO4)--- 30 Zinc borate (ZnBrOq) Copperborate (CuBrOq) The above are dissolved in a 10% solution of aqueousammonia.

In the above solution the ammonium hydroxide serves to form the complexions of the copper and zinc salts and subsequently, when the Wood isimpregnated with the above solution, the ammonia evaporates and thevarious metal salts and their hydroxides, as given above, areprecipitated and/ or deposited in the wood. Under these conditions thehydroxides render the salts unleachable, due to the reprecipitation ofthe soluble products liberated in the process of the hydrolysis. At thesame time the basic copper ammonium complex (Cu(NH3)4(OI-I)2) due to itssolvent action on the cellulose of the wood, causes the wood to be morethoroughly impregnated.

By way of further explanation it should be added that while the aboveidentified metal salts are insoluble and form a good preservative, andcan be used without their hydroxide, the addition of the hydroxide ofthe particular salts renders them more lasting and effective, due to thechemical actions described above.

In the application of my invention to the impregnation of finishedlumber, particularly where it may be used without paint, the metalsalts, suggested above, may be chosen so as to avoid discoloration ofthe wood upon impregnation. For example, when a colorless preservativeis required, it is recommended that the zinc salts be used, whereas inthe event that the effect of the preservative upon the wood, insofar asdiscoloration is concerned is of no moment, any one or all combinationsof the above recommended salts may be used.

While I have, for the sake of clearness and in order to disclose myinvention so that the same can be readily understood, described specificingredients and combinations thereof, I desire to have it understoodthat this invention is not necessarily limited to the specificingredients and combinations set forth, but may be embodied in otherways that will suggest themselves to persons skilled in the art. It isbelieved that this invention is new and it is desired to claim it sothat all such changes as come within the scope of the appended claimsare to be considered as part of this invention.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. The improvement in an impregnating material ior the preservation ofWood-employing an ammoniacal solution ,of copper and zinc salts whichcomprises providing in the solution a water insoluble hydroxide of saidsalts to reprecipitate the hydrolyzable products of the impregnatingsalts in the event of leaching.

2. The improvement in an impregnating material for the preservation ofwood employing an ammoniacal zinc borate solution which comprisesproviding an excess of zinc hydroxide to reprecipitate the hydrolyzableproducts of the zinc borate in the event of leaching.

3. The improvement in an impregnating material for the preservation ofwood employing an ammoniacal copper borate solution which comprisesproviding an excess of copper hydroxide to reprecipitate thehydrolyzable products of the copper borate in the event of leaching.

4. The improvement in an impregnating material for-the preservation ofwood employing an ammoniacal zinc salt solution which comprisesproviding an excess of zinc hydroxide to reprecipitate the hydrolyzableproducts of the zinc salts in the event of leaching.

5. The improvement in an impregnating material for the preservation ofwood employing an ammoniacal copper salt solution which comprisesproviding an excess of copper hydroxide to reprecipitate thehydrolyzable products of the copper salts in the event of leaching.

6. A composition of the character described for the preservation ofwood, consisting of 10% CuCO3-,Cu(OH)z; 10% ZnCOaZn(OH)2; 30% CllNHiPOt;30% ZnNI-I4PO4; 10% ZnB4O7; 10% (31115407; dissolved in aqueous ammonia.

AARON GORDON.

